Referring to FIGS. 1 and 2, a perspective view of an interior of a conventional projection apparatus 2 is shown. The conventional projection apparatus 2 includes a light source device 4, a projection lens 6 and a casing 8 covering an optical path between the light source device 4 and the projection lens 6. An integration rod module 10 is disposed within the casing 8, and in the optical path.
A rod cover 12 is disposed securely on one side of the casing 8 adjacent to the light source device 4 such that light beams emitted from the light source device 4 pass through a light aperture of the rod cover 12. Besides, the light beams enter from the front of the integration rod module 10 into the projection lens 6.
The integration rod module 10 includes an integration rod 1002 extending along the optical path and a holder 1004 enclosing the integration rod 1002 therein. Generally, a positioning device 16 is installed in the projection apparatus 2 to position the integration rod module 10 within the casing 8.
Referring to FIG. 3, the positioning device 16 includes an upper flexible element 18 and a lower flexible element 19. The upper flexible element 18 has an intermediate section fixed to an upper inner surface of the casing 8, and two ends extending from the intermediate section to front and rear ends of the integration rod module 10 respectively. The ends of the upper flexible element 18 have elasticity to press against an upper surface of the holder 1004 and the elasticity provides a balance force that presses against a lower interior surface of the casing 8 to support a lower surface of the holder 1004. Thus, the integration rod module 10 is retained between the upper and lower interior surfaces of the casing 8.
In addition, the lower flexible element 19 is disposed within the lower surface of the holder 1004, and one elastic end of the lower flexible element 19 extends downwardly. The elastic end presses against a longitudinally extended bottom part 802 of the lower surface of the casing 8 to provide a force in a direction from the integration rod module 10 to the rod cover 12. Thus, the force in the direction from the integration rod module 10 to the rod cover 12 balances a support force that the rod cover 12 presses against the front end of the integration rod module 10. The integration rod module 10 is indeed positioned within the casing 8.
As shown in FIG. 3, a counterclockwise torque M caused by the lower flexible element 19 causes the integration rod module 10 to uplift, and then the front end of an integration rod 1002 presses against the rod cover 12 tightly. It leads to the incorrect position of the integration rod 1002, and concentrates stresses on the front end of the integration rod 1002 to cause damage to the integration rod 102.
Moreover, the torque M counteracts and cancels out a portion of the elasticity of the upper flexible element 18. After assembly of the conventional projection apparatus 2, the integration rod module 10 is easy to be displaced in case of receiving a terrible vibration or shock. Since one front end of the integration rod module 10 is in tight abutment against the rod cover 12, it is relatively difficult for the same to retrieve the initial position of the integration rod 10 within the casing 8. Displacement of the integration rod 1002 degrades the light projection ability of the conventional projection apparatus 2.